Electrically triggered squib



June 28, 1966 T. TOGNOLA ELECTRICALLY TRIGGERED SQUIB Original Filed Oct. 19, 1961 .lulllllr lll lllIIlll INVENTOR.

TULLlO TOGNOLA 3Y6 M ATTOR IZS 3,257,946 ELECTRICALLY TRIGGERED SQUIB Tullio Tognola, Sidney, N.Y., assignor to The Bendix Corporation, a corporation of Delaware Continuation of application Ser. No. 146,146, Oct. 19,

- 1961. This application July 16, 1964, Ser. No..388,029

20 Claims. (Cl. 102-28) trical energy of radio frequency.

A further object of the invention lies in the provis'on of a squib of the character indicated which can be fired only upon itssubj'ection to a triggering pulse having a predetermined voltage and energy content.

Another object of the invention lies in the provision of an electrically triggered squib which can readily be tested in either its unloaded or loaded condition, and

in its loaded condition can be tested being fired.

Still another object of the invention lies in the provision of an electrically trigged squib which is simple and rugged in construction and which is economically made.

The above and further objects and novel features of the invention will more fully appear from the following detail description when the same is read in connection with the accompanying drawings. It is to be expressely understood, however, that the drawings are for the purpose of illustration only and are not intended as a definition of the limits of the invention.

In the drawings, wherein like reference characters refer to like parts throughout the several views,

FIG. 1 is a view in axial section through a preferred without danger of embodiment of the squib of the invention, certain of the parts being shown in elevation;

FIG. 2 is a view in transverse section through the illustrative embodiment of the squib, the section being taken along the line 2--2 of FIG. 1; and

FIG. 3 is a view in transverse section through the illustrative embodiment of the squib, the section being taken'along the line 3-3 of FIG. 1.

The squib of the present invention is adapted for use, for example, to initiate functions as during the flight of a missile. For safe, dependable operation of the squib it is necessary that it be fired only upon the reception of a triggering pulse of a predetermined character.

a Prior electrically triggered squibs have conventionally included one or more small gauge resistance wires disposed in proximity to explosive materials such as powder, the wire or wires being adapted to be heated to incandescence upon the reception of a triggering signal by the squib. Squibs of such prior construction are subject to a number of disadvantages, including the possibility of open circuit due to the breakage of the resistance wire or wires, unreliability due to inconsistency of soldering or welding of the fine wire or wires to the conductors, and a dudding of the powder by its subjection to a high temperature in the proximity of the resistance wire or 'wires, such high temperature being insulficient, however,

to cause the firing of the powder. Perhaps the'most serious difiiculty encountered with squibs of such prior construction has been their unintentional or accidental firing because of their susceptibility to radio frequency radiation. The loop composed of the conductors and the fine resistance wire or wires is prone to the reception of radiation of radio frequency and the generation of currents in the loop through an induction effect of high United States Patent quency received thereby, will not be triggered by being subjected to high ambient temperatures on the order of 600 F., will not be fired by being connected to a source of electrical energy ordinarily present in a vehicle suchas a missile other than in the triggering circuit, and can be fired only by being subjected to a triggering pulse having a predetermined minimum voltage and energy content. 4

Turning now tothe drawing, the illustrative embodiment of squib made in accordance with the invention is designated as a whole by the reference character 10. Such squib, which is of generally circular cylindrical shape, has a ceramic electrically insulating body 11 at one end thereof. From such end of the squib, spaced from each other and lying parallel to the long'tudinal axis of the squib, there project two conductors which may be made in the form of contact pins adapted to interfit with socket contacts of a separable electrical connector part (not shown). A first one of such pins, designated 12, extends inwardly throughv a passage 14 in body 11, the inner end of the pin being enlarged to form a head 15 which functions as one electrode of a spark gap. Head 15 snugly fits within a cavity 16 in body 11, the engagement between head 15, the walls of cavity 16, and that between pin 12' and passage 14 being such as substantially to prevent the passage of air through the interfaces between such members.

The electrode 15 is in-the form of a cup having an axially directed circular cylindrical seat 17 therein, said seat snugly receiving one end of a circular cylindrical ceramic body 19 therein. In a preferred embodiment the body 19, which functions as an electrode spacer, is

made of alumina or quartz, such body being provided with an electrically semiconductive coating over its external surface. Such semiconductive coating may, for example, be of the type disclosed and claimed in the patent to Harris, No. 2,953,704.

The left-hand end of cavity 16 (FIG. 1) terminates in a plane transverse tothe longitudinal axis of the squib and coplanar with an extended circular flat surface 29 on body 11. The peripherally outer portion of body 11 extends to the left of surface 20 to form a peripheral axially extending outer flange 24. There is thus formed by surface 20 and flange 24 an extended seat 25 in the left-hand end of body 11. Positioned within such seat as shown is a plate-like member 26 in the form of a circular cylindrical disc. Member 26, which is made of electrically conducting metal, has a second contact pin 21 connected thereto and positioned parallel to pin 12. As shown, the inner end of pin 21 extends through a hole 29 in member 26, the pin being secured to member 26 as by an annular weld 30. Pin 21 extends through and substantiallysealingly contacts a passage 22 in body 11.

Positioned in seat 25 between member 26 and surface 20 is a thin imperforate sheet of electrically conducting metal 27, sheet 27 overlying the left-hand end of cavity 16 and firmly engaging the left-hand end of member 19, which lies coplanar with surface 20. Sheet 27 has secure electrical contact with member 26 throughout its extent; elements 26' and 27 together constitute a second electrode between which and electrode 15 there occur spark discharges when the contact pins 12 and 21 are connected to a source of electrical energy having a predetermined voltage and energy content.

The squib of the invention is substantially immune to the effects of energy of radio fre- Member 26 is retained in seat 25 by a spring ring 31 as shown. Member 26 has a passage 32 therethrough, such passage being aligned with and having substantially the same diameter as the body 19. The remaining space within seat 25, outwardly of member 26 is filled with a charge of explosive material 39, which may be a spark ignited explosive priming powder. Such powder extends within passage 32 into contact with the outer face of sheet member 26 as shown at 38.

The squib is provided with a circular cylindrical sheath 36 which may be made, for example, of copper or brass. The sheath has a shallow annular shoulder intermediate its length which engages the left hand peripheral edge of body 11 as shown in FIG. 1. The sheath is retained on the squib by having its right hand end spun over the end of body 11 to form a shallow inwardly directed flange 37.

Within the outer end portion 34 of sheath 36 there is disposed the main charge 4-0 of explosive material which may be in the form of explosive powder. Charge 40 is retained within the squib by a disc-shaped closure mem ber 41 which is received within and secured to an annular seat 42 in the end of portion 34 of the sheath. The squib thus provides a housing made up of elements 11, 36, and 41, such housing providing a first, gas-filled cavity 16 and a second cavity containing an ignitable charge' 39, 40 therein.

As above noted, the space within cavity 16 is substantially sealed against the egress of air. When the contact pins 12 and 21 are subjected to electrical energy of spark discharge intensity, a spark discharge occurs between the left-hand end of electrode 15 and the portion of sheet 27 adjacent the end of body 19. When such spark discharge is of a predetermined intensity, it produces a heating of the air in cavity 16 sufiicient to burst the portion of sheet 27 which overlies the inner end of passage '32. Thereupon the priming powder 39 is placed in operative contact with the spark discharge so as to be ignited thereby. Ignition of charge 39, in turn, ignites and produces the explosion of the main charge 40 so that the squib produces power to perform its function.

The sheet member 27 may, for example, be madeof a foil of a metal such as aluminum, copper, and the like. Sheet 27 may have a thickness which is chosen according to the level of energy selected for its rupture. The thickness of sheet 27 may, for example, vary between .0005- to .005 inch.

Although the body 11 has been described as being made of a ceramic material, it may, for example, be

made of electrically insulating plastic material when the r squib is employed for low temperature applications. If the body 11 is made of a moldable material, the parts 15, 19, 21, 26, and 27 may be preliminarily assembled and molded into body 11 in the form of inserts therein.

The squib of the present invention is immune to being fired by the application of electrical energy at low voltages between conductors 12 and 21. This results from the fact that the current conducted through or over the semiconductive coating on body 19 is very small, and there is thus insufficient heat and hence, insuflicient pressure generated to cause the sheet 27 to rupture. Sheet 27 will also not be ruptured should high voltage sparks of low energy value occur between electrode 15 and sheet 27.

The squib of the invention may be tested in the unloaded condition by subjecting the spark gap to spark discharges of such energy level that the sheet 27 does not rupture. In such test, the occurrence of a spark discharge between the two electrodes of the squib may be detected by either visual observation of the movement of the portion of sheet 27 exposed through passage 32, or by detecting the sound which accompanies such spark discharge. Tests upon a loaded squib may be carried out with the aid of sound pick-up apparatus which a1- vlike, as well as in the suggested manner of use of the apparatus of the invention, may be made without departing from the spirit and scope of the invention as will now be apparent to those skilled in the art. Thus, although the body 19 has been described as being made with an electrically nonconducting core with a semiconductive coating thereon, the body 19 may, if desired, be formed entirely of electrically semiconductive material.

What is claimed is:

1. An electrically triggered squib, which comprises opposed spaced electrodes forming a spark discharge gap, means forming a substantially closed gas-filled cavity of substantial size between the electrodes, a spark ignitable charge of explosive material positioned adjacent the cavity, and a thin frangible sheet forming a part of the cavity-forming means and separating the explosive material from the spark gap, the sheet being ruptured by expansion of the gas within the cavity upon a spark discharge of predetermined intensity at the spark gap, whereby to afford access between the explosive material and the spark gap.

2. An electrically triggered squib comprising opposed spaced electrodes forming a spark discharge gap, means forming a substantially closed gas-filled cavity of substantial size between the electrodes, a spark ignitable charge of explosive material positioned adjacent the' cavity, and a thin frangible electrically conductive sheet forming a part of one of said electrodes and a part of the cavity-forming means and separating the explosive material from the spark gap, the sheet being rupturable by expansion of the gas within the cavity upon a spark discharge of predetermined intensity at the spark gap, whereby to afford access between the explosive material and the spark gap.

3. A squib as defined in claim 2, wherein said sheet is positioned spaced from the other electrode so that the spark discharge initially occurs between the other of said electrodes and the sheet.

4. An electrically triggered squib, which comprises opposed spaced electrodes forming a spark discharge gap, means forming a substantially closed gas-filled cavity of substantial size between the electrodes, a first one of said electrodes including an electrically conductive broad plate-like member positioned outwardly of the cavity at one end thereof, said plate-like member having a passage therethrough generally normal to the broad extent of the member, a second of said electrodes being positioned in the cavity spaced from the platelike member and disposed generally normal to the member and generally in alignment with the passage in such member, a thin frangible sheet overlying and intimately contacting the first broad surface of the member and forming a part of the cavity forming means confronting the second electrode, and a spark ignitable charge of explosive material positioned adjacent the second surface of the plate-like member, the sheet being rupturable by expansion of the gas within the cavity upon a spark discharge of predetermined intensity at the spark gap, whereby to afford access through the passage through the plate-like member between the explosive material and the spark gap.

5. A squib as defined in claim 4, comprising an electrode-spacing member having a portion with a cross section of substantially the same shape and size as the passage interposed between the electrodes, at least generally aligned with the passage, and closely overlying the sheet.

6. A squib as defined in claim 5, wherein the frangible sheet is electrically conductive and is electrically connected to the electrode-spacing member.

7. A squib as defined by claim 6, wherein the electrode-spacing member is interposed between and abuts the second electrode and the frangible sheet, the electrode-spacing member being such as to provide an electrically semiconductive path between the second electrode and the frangible sheet.

8. An electrically triggered squib, which comprises a housing, said housing having a first cavity therein, a first electrode disposed in the housing at one end of the cavity, a second electrode disposed in the cavity spaced from the first electrode, said first electrode comprising an electrically conductive thin frangible sheet disposed across and closing the end of the first cavity, the cavity presenting a gas-filled space of substantial volume therewithin between the electrodes, the housing having a second cavity therein disposed beyond the sheet on the side thereof opposite the second electrode, and a spark ignitable charge of explosive material in the second cavity, the sheet being rupturable by expansion of the gas within the first cavity upon a spark discharge of predetermined intensity between the electrodes, whereby to afford access between the explosive material and the the gap between the electrodes.

9. A squib as defined by claim 8, wherein the portion of the housing containing the first cavity is electrically insulating.

10. A squib as defined by claim 9, wherein the first electrode comprises an electrically conductive metal plate member disposed across the end of the first cavity, the sheet is interposed between the plate member and the second electrode and has intimate contact throughout its broad extent with the plate member, and the plate member has a passage therethrough generally aligned with the second electrode.

11. A squib as defined by claim 10, wherein the sheet is electrically conductive and forms the portion of the first electrode most closely approaching the second electrode.

12. A squib as defined by claim 11, wherein the plate member is laterally extended beyond the first cavity, and comprising a first conductor connected to and extending from the plate member through the electrically insulating portion of the housing at one side of the first cavity, and a second conductor connected to and extending from the second electrode through the electrically insulating portion of the housing at a location laterally spaced from the first conductor.

13. A squib comprising means forming a substantially sealed gas-filled cavity and a second cavity adjacent thereto, a charge of spark ignitable material in the second cavity, said means comprising a thin frangible sheet forming a wall section common to both of said cavities, and means comprising spaced electrodes forming a spark gap in said gas-filled cavity, said sheet being rupturable by expansion of the gas within the gas filled cavity upon a spark discharge of at least predetermined minimum intensity at the spark gap, whereby to afford access between said cavities and to permit ignition of the ignitable material in the second cavity by the spark discharge.

14. A squib as defined in claim 13 wherein the means forming the spark gap comprises a semiconductive surface in said gas-filled cavity connecting said electrodes at the spark gap.

15. -A squid comprising means forming a substantially sealed gas-filled chamber, said means including a thin frangible sheet closing one end of the chamber, and means forming a spark gap within said chamber, said sheet being rupturable by the thermal expansion of the gas in said chamber only upon a spark discharge at the spark gap of at least predetermined minimum intensity.

16. A squib as defined in claim 15, wherein the spark gap is a shunted surface gap comprising electrodes bridged by a semiconductive surface.

17. In a squib, means forming a shunted surface spark gap including spaced electrodes and semiconductive means bridging the gap between said electrodes, and means for forming a substantially sealed gas-filled chamber containing said gap, at least a portion of the wall of the chamber being constituted by a thin frangible sheet which is rupturable by gaseous pressure generated in said chamber by the heat of a spark discharge at the spark gap of at least predetermined intensity.

18. An electrically triggerable squib which comprises means forming a substantially closed gas-filled chamber of substantial size, spaced electrodes forming a spark discharge gap in said chamber, a spark ignitable charge of explosive material positioned adjacent the chamber, and a thin frangible sheet constituting a part of the chamber-forming means and separating the explosive material from the spark gap, the sheet being rupturable by expansion of the gas within the chamber upon a spark discharge of predetermined intensity at the spark gap, whereby to atford access between the explosive material and the spark gap.

19. An electrically triggerab-le squib which comprises a housing having a gas-filled cavity of substantial volume therein, a first electrode disposed in the housing at one end of the cavity, a second electrode disposed in the cavity in spaced relation to the first electrode to form a spark gap, thin frangible sheet disposed across and closing an end of the cavity, the housing having a second cavity therein disposed beyond the sheet on the side thereof opposite said spark gap, and a spark ignitable charge of explosive material in the second cavity, said sheet being rupturable by expansion of the gas within the firs-t cavity upon a spark discharge of predetermined intensity between the electrodes, whereby to afford access between the explosive material and the spark gap between the electrodes.

20. A squib as defined by claim 19, wherein said first electrode and said frangible sheet are at opposite ends of the first cavity.

References Cited by the Examiner UNITED STATES PATENTS 2,996,944 8/1961 Chessin et al. 86--l 3,019,732 2/1962 Kaspaul 10228 3,100,447 8/1963 Bet-ts 10228 BENJAMIN A. BORCHELT, Primary Examiner.

R. V. LOTTMANN, Assistant Exa'miner. 

1. AN ELECTRICALLY TRIGGERED SQUIB, WHICH COMPRISES OPPOSED SPACED ELECTRODES FORMING A SPARK DISCHARGE GAP, MEANS FORMING A SUBSTANTIALLY CLOSED GAS-FILLED CAVITY OF SUBSTANTIAL SIZE BETWEEN THE ELECTRODES, A SPARK IGNITABLE CHARGE OF EXPLOSIVE MATERIAL POSITIONED ADJACENT THE CAVITY, AND A THIN FRANGIBLE SHEET FORMING A PART OF THE CAVITY-FORMING MEANS AND SEPARATING THE EXPLOSIVE MATERIAL FROM THE SPARK GAP, THE SHEET BEING RUPTURED BY EXPANSION OF THE GAS WITHIN THE CAVITY UPON A SPARK DISCHARGE OF PREDETERMINED INTENSITY AT THE SPARK GAP, WHEREBY TO AFFORD ACCESS BETWEEN THE EXPLOSIVE MATERIAL AND THE SPARK GAP. 